The advantages of digital processing have motivated efforts on high-dynamic-range-enabled digital imaging systems in order to take the place of traditional film-based imaging technology. Most widely used video coding standards utilize three color components (red, green, blue) to specify the color information. Compared with conventional eight bit representation for a single color component of one pixel in an image, an enhanced dynamic range requires more than eight bits to represent one color component of one pixel. With the development of high bit-depth color techniques, the issue of backward compatibility to the existing eight bit depth has emerged. Solutions to this issue are highly desired, since new compression and storage techniques, transmitting methods, playback devices, and display devices for eight bit depth and high bit-depth are required.
Further, the capability of providing different color bit depths of a single video content within a single bit-stream is of particular importance to different terminal display capabilities during multimedia content deliveries. One solution for backward compatibility to eight bit depth is color bit depth scalability. A possible framework for color bit depth scalable video coding is shown in FIG. 1. Two input video sequences describe the same scene, but have different color bit depth: usually M=8 while N=10, 12, or 16. The M-bit input is encoded as the base-layer. At the terminal, a standard display device (Std Display) can use the decoded base-layer for displaying.
More visual information of the N-bit input is encoded in the enhancement-layer. If a terminal has a high quality display device (HQ Display), the decoded enhancement-layer together with the decoded base-layer provides the complete information to display the N-bit video sequence. In this case, inter-layer prediction as shown in FIG. 1 impacts significantly the coding efficiency.